The present invention relates generally to control electronic devices, and more particularly to intelligent industrial control devices such as Programmable Logic Controllers (PLCs).
PLCs generally consist of a system power supply, Input/Output (I/O) interfaces, and an intelligent control section that may or may not contain a microprocessor. Some PLCs may be modular in design, such that the control, power supply, and I/O sections, and sometimes the interconnect between these sections, are all separate physical modules that may be interchanged. Some PLCs include electromechanical cooling devices, such as fans or liquid cooling systems for example, to transfer heat away from the heat-generating electronic components enclosed therein. However, some customers that purchase PLCs may prefer not to have such electromechanical cooling devices in their PLC systems for various reasons. These reasons may include, but are not limited to, concerns about the reliability of the cooling device, required regularly scheduled maintenance to clean or replace filters of the cooling device, required regularly scheduled maintenance to lubricate various mechanical components of the cooling device, and concerns relating to excessive heat generation in the event of a malfunctioning cooling device. Electronic components, including those found in PLC systems, generate heat and have manufacturer-dictated ratings on how hot the components may become. The need to remove heat from the PLC and the customer requirement of not using an electromechanical cooling device places limitations on how much heat the PLC components may generate, how high the ambient temperature is allowed to be in the PLC's operating environment, how physically small the PLC modules may be, and thus how much performance and what available features the PLC is capable of delivering.
Accordingly, there is a need in the art for electronic control devices, and particularly PLCs, having a heat transfer arrangement that overcomes these drawbacks.